Principles of Neurophysiology

What are the two major subdivisions of the mammalian nervous system?

-Central Nervous System (CNS): brain, spinal cord

-Peripheral Nervous System (PNS): afferent (sensory) and efferent (motor → somatic & autonomic)

What are the main parts of a motor neuron?

Dendritic zone, cell body (soma), axon, presynaptic terminal.

What is the difference between nuclei and ganglia?

Nuclei = clusters of cell bodies in the CNS

Ganglia = clusters in the PNS.

How are neurons classified morphologically?

Multipolar: most common

Unipolar: spinal & cranial ganglia

Bipolar: retina, auditory nerve, olfactory epithelium

What cells myelinate neurons in the PNS vs CNS?

Schwann cells (PNS) and oligodendrocytes (CNS).

What are nodes of Ranvier?

Gaps between myelin internodes where the axon membrane is exposed, enabling saltatory conduction.

What are the main functions of astrocytes?

Form glial membranes, regulate fluid/electrolyte balance, maintain BBB, remove excess neurotransmitters, repair CNS injury.

What are microglia?

CNS macrophages; remove debris and proliferate after brain injury.

What do ependymal cells do?

Line ventricles and central canal; form a barrier between CNS and CSF; line choroid plexus (secrete CSF).

What are the six anatomical regions of the CNS?

Telencephalon, diencephalon, midbrain, pons, medulla, spinal cord.

What are the main functions of the hippocampus?

Memory consolidation and spatial learning.

Which disease is associated with degeneration of substantia nigra neurons?

Parkinson's disease.

What is the resting membrane potential of neurons?

About -70 mV, due to Na⁺/K⁺ ATPase and K⁺ leak channels.

What is an EPSP vs IPSP?

EPSP = excitatory depolarization toward threshold

IPSP = inhibitory hyperpolarization away from threshold.

What is summation?

-Spatial summation = graded potentials from multiple synapses

-Temporal summation = repeated signals from one synapse

What is the refractory period?

Time during which a neuron cannot generate another AP (absolute), or needs a stronger stimulus (relative).

How does myelination affect AP conduction?

Increases speed via saltatory conduction (AP jumps from node to node).

Which nerve fiber type is fastest? Slowest?

Fastest = Aα (somatic motor, proprioception); Slowest = C fibers (pain, temperature, postganglionic autonomic).

Name major excitatory and inhibitory neurotransmitters.

Excitatory: Acetylcholine, glutamate, norepinephrine (some contexts)

Inhibitory: Glycine, GABA, dopamine (often inhibitory)

How are neurons named?

By their neurotransmitter (e.g., cholinergic, adrenergic, GABAergic).

What are the two types of cholinergic receptors?

Nicotinic (ionotropic) and muscarinic (M1-M3, metabotropic).

What is the sequence of neurotransmitter release?

AP → Ca²⁺ influx → vesicle fusion via SNARE proteins → neurotransmitter release.

What are examples of SNARE proteins?

Synaptobrevin, synaptotagmin (vesicle); SNAP-25, syntaxin (presynaptic membrane).

What receptor type is found at the neuromuscular junction?

Nicotinic acetylcholine receptors (ligand-gated Na⁺ channels).